Theftproof electric-light bulb



D. R. COUGHLIN. THEFTIIJROOF ELECTRIC LIGHT BULB.

APPLICATION FILED OCT. 28. I920.

Patented Dec. 5, 1922.

Patented Dec. 5, 1922.

FFICE.

DANIEL R. COUGHLIN, OF DES MOINES, IOWA.

'rmnr'rraoor ELECTRIC-LIGHT BULB.

Application filed October 28, 1920. Serial No. 420,089.

T all whom it may concern Be it known that I, DANIEL R. CoUGHmN, a citizen of the United States, and a resident of Des Moines, in the county of Polk and State of Iowa, have invented a certain new and useful Theftproof Electric-Light Bulb, of which the following is a specfication.

The object of my invention is to provide an electric light bulb of simple construction, so made that it may be inserted into a socket for making proper circuit connect-ions in the ordinary way, and then can not be stolen or removed from the socket.

With this and other objects in view, my invention consists in the construction, arrangement and comb-inationof the various parts of my device, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims, and illustrated in the accompanying drawings, in which: y i

Figure 1 shows a side elevation of an electric light bulb embodying my invention,

arts being shown in section.

Figure 2 shows a top or'plan view of the same. 7

Figure 3 shows a horizontal, detailed, sectional view taken on the line 3-3 of Figure 1; and

Figure 4 shows a horizontal, detailed, sectional view taken on the line 4-4: of Figure 1. I

It is well-known that railroad companies and others suffer substantial losses on account of the theft of electric light bulbs or globes, which are taken from stations, cars and other places to which the public has access.

It is so easy to remove the ordinary bulb from the socket, that it is found that places of the kind mentioned, empty houses and other places, are frequently robbed of these bulbs and the aggregate losses suffered in the country at large are great.

It is my purpose to provide a bulb. which can be used in the ordinary way with the or dinary socket, and which when once installed in the socket can not be removed until the filament has burned out.

In the accompanying drawings, I have used the reference numeral 10 to indicate the body of an electric light bulb or globe, which is of ordinary construction. At the smaller end of the bulb or globe 10, the glass is extended in substantially cylindrical form away from the body, as at 11.

The contact member 22. stood, is insulated from the shell contact 18 At the point of juncture between the body 10 and the cylindrical extension 11, there is provided an annular groove or recess 12. In the exterior surface of the body 10 near the groove 12, there is provided a smaller annular groove 13.'the purpose of which will be hereinafter more fully referred to.

The filament lead or current conduct-ing member in the bulb is extended laterally through the wall of the extension 11, as at 14 and a drop of solder orthe like 15 is placed on the outer end of the lead 14;, outside of the glass of the member 11. The other filament lead or conducting member 14 is extended longitudinally through the member 11, and has a similar drop 16 of solder or conducting material outside the member 11. It will, of course, be understood that the filament 11f is connected with the leads 1 1 and 1 1 The member 11 is formed with a longitudinal groove 17 in its exterior side wall,

as shown in Figures 2 and 3, and a metal casing 18 commonly called a threaded shell contact is provided, and is formed with spiral screw-threads 19, as is the case in ordinary electric light bulbs, and is arranged to be extended over the member 11.

In the installation of the shell contact 18, soft plaster of Paris or the like 20 is placed in the groove 17 when the casing is placed in position, and this plaster of Paris will rapidly harden for holding the shell contact 18 against rotation on the member 11.

The lower'end or edge of the shell contact 18 is crimped or bent inwardly until it is received in the groove 12, as illustrated at 21.

Extending through the shell contact 18 is a contact member 22, which will contact with the drop 16. which forms a contact member.

it will be underin the ordinary way. i

In the practical use of my improved theft proof bulb. the bulb is screwed into the socket in the ordinary way, until the contacts are made, then the bulb is given an additional turn for breaking the plaster bond 20.

It will then be seen that if a thief should attempt to unscrew the bulb and remove it, the glass portion will rotate freely in the casing 18 and can not be removed. The bulb is then used until the filament is burned out.

Thereupon the bulb body may be struck sharply, and it will break cleanly along the line of the groove 13. Thereafter access may be had to the interior of the member 11 with the fingers or with a suitable tool, and the shell contact 18 may be unscrewed from the socket and removed, for permitting the installation of a new bulb.

The saving to be accomplished by using the bulb of the type herein shown is obvious from theforegoing description. v

Changes may be made in the construction of my device, and it is my intention to provide and cover by the patent to be issued hereon, a-device comprising an electric light bulb, so arranged that when it is once installed in the socket, it can not be removed without breakage, and it is my purpose to cover by my claims, any modified forms of structure or use of mechanical equivalents, which may be reasonably included Within their scope.

I claim as my invention:

1. An electric lamp comprising a bulb body having an extension, a threaded shellcontact mounted on said extension provided with an insulated center contact, said shell contact and bulb body being provided with means to prevent longitudinal separation and to permit relative rotation therebetween, a filament in said bulb, means for maintaining connection between said filament and said shell and center contacts during relative rotation of said contacts and the bulb body and frangible means, between said shell-contact and said extension to normally prevent relative rotation therebetween.

2. An electric lamp, comprising a bulb, a shell contact having an insulated center contact mounted thereon, said shell contact and bulb being provided with means to preventlongitudinal separation and; to permit relative rotation therebetween, a filament in said bulb, means for malntainlng connection between said filament and said shell and center contacts during relative rotation of said contacts and the bulb, and frangible means between said shell contact and said bulb to normally prevent relative rotation therebetween.

Des Moines, Iowa, October 9, 1920.

DANIEL R. COUGHLIN. 

